<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<body>
<div id="app">
  <input type="text" :value="message" @input="message = $event.target.value">
  {{message}}
</div>

<script src="./js/vue.js"></script>

<script>
  const app = new Vue({
    el:'#app',
    data:{
      message:'Hello World'
    },
    methods:{
      valueChange(event){
        this.message = event.target.value;
      }
    }
  });
</script>
</body>
</html>